The present invention relates to a device for measuring a physical quantity associated with the rotation of a member and to methods for checking this device.
It applies in particular to the measurement of a physical quantity associated with the rotation of a bogie axle of a railway vehicle.
In the prior art, a device is already known for measuring a physical quantity associated with the rotation of a member, which comprises a metal disc integral with the rotating member and provided with at least one aperture forming a reference point.
In the case of a bogie of a railway vehicle, the disc is integral with one axle (rotating member).
Conventionally, the measurement device delivers a physical quantity associated with the angular displacement of the disc, which makes it possible to calculate in particular the distance travelled by the railway vehicle or else the speed of this vehicle.
Usually, the measurement device includes an optical detection assembly and is in the form of a preassembled module intended to be mounted on a free end of a bogie axle. The optical detection assembly and the disc are protected from dust and dirt by suitable sealing means. Such a preassembled module may advantageously be fitted onto a bogie without dismantling the latter.
In some cases, mounting the preassembled module on the free end of a bogie axle is prevented or impossible. However, it is difficult to adapt such a module in order to allow it to be fitted onto another part of the axle, this being in particular for reasons of difficult mounting, of lack of space and/or of protection against water, dust and dirt which are liable to interfere with the correct operation of the optical detection assembly.
The object of the invention is especially to propose a device allowing reliable measurement of a physical quantity associated with the rotation of a bogie axle, this measurement device being moreover easy to fit onto the bogie.
For this purpose, the subject of the invention is a measurement device of the aforementioned type, characterized in that it comprises a fixed assembly for detecting this reference point, comprising at least one magnetic proximity detector and means for checking that this detector is operating correctly, these means being fitted outside the magnetic detector, without electrical contact or connection with the latter.
According to other characteristics of this measurement device:
the checking means comprise at least one conducting turns which surrounds an active end of the detector and is connected to means of modifying its state by short-circuiting this turn or by supplying it with current;
the checking means comprise a conducting coil, consisting of several turns, which surrounds an active end of the detector and is connected to means of modifying its state by short-circuiting this coil or by supplying it with current;
the magnetic detector is an inductive proximity detector;
the disc comprises n apertures uniformly distributed over a circle centred on its axis and the detection assembly comprises p inductive detectors uniformly distributed over a circular arc opposite the apertures, the dimensions and the angular spacings of the apertures and of the detectors being such that there is always a detector opposite an aperture whatever the angular position of the disc with respect to the detection assembly;
the rotating member is a bogie axle of a railway vehicle.
The subject of the invention is also a method of checking the measurement device defined above, characterized in that the state of the turn or of the oil of the detector in operation is modified according to a reference sequence and this reference sequence is compared with the signal output by this detector.
The subject of the invention is also a method of controlling the measurement device defined above, characterized in that, with the disc being unable to move with respect to the detection assembly, the state of the means of checking at least one detector in operation and opposite an aperture is modified according to a reference sequence and this reference sequence is compared with the signal output by this detector opposite an aperture.